The present invention relates to a wire bonding apparatus, and in particular to a wire bonder capable of preventing oxidation of a wire when applying a copper wire in order to enhance the bonding force and the mechanical strength of wiring material for use in semiconductor devices.
It is generally well known in the art that upon wiring operation between a chip and a pad of a lead frame during a semiconductor manufacturing process, there are used a ball bonding method bonding by forming a ball at a free end of a wire or a heat-press bonding method bonding directly the wire to the pad, of which the ball bonding method is preferred, as it not only makes a bonding area wider but also provides more stable bonding, rather than the heat-press bonding method.
A known bonding apparatus, as shown in FIG. 1, is constructed such that a wire 20 is wound into a spool 2 being isolated from an outer atmosphere by a cover 1, and it is drawn out through a take-out tube 3 at a center thereof, being supported and guided by a plurality of clamps 4. Thereafter, the wire passes through a capillary device 5 disposed adjacent to the clamp, said capillary device carrying out the wiring operation by moving between the lead frame and the chip pads. However, such a known wire bonding apparatus has a disadvantage that its spool mounter may not provide a complete wire shield from the atmosphere, thereby causing a considerable oxidation of the wire. Upon this bonding operation, as a gold wire is generally used for several days, it has become a factor increasing the manufacturing cost of a semiconductor chip. Further, there has been a problem that the yield eventually decreases because the wire droops or extends due to the heat being applied during a packaging process. Moreover, even though using a copper wire of higher mechanical strength in order to solve the problem, there still remains a problem that the copper wire is easily oxidized at high temperature, thereby affecting its bonding strength.